\begin{tikzpicture}[>=Stealth, scale=0.8]
    \draw [very thick] (0, 4) circle (0.6) node {甲地};
    \draw [very thick] (6, 4) circle (0.6) node {乙地};
    \draw [very thick] (6, 0) circle (0.6) node {丙地};
    \draw [very thick] (0, 0) circle (0.6) node {丁地};

    \draw [->] (0.5, 4.3) -- (5.5, 4.3);
    \draw [->] (0.5, 3.7) -- (5.5, 3.7);

    \draw [->] (5.7, 3.5) -- (5.7, 0.5);
    \draw [->] (6, 3.4) -- (6, 0.6);
    \draw [->] (6.3, 3.5) -- (6.3, 0.5);

    \draw [->] (-0.3, 3.5) -- (-0.3, 0.5);
    \draw [->] (-0.1, 3.4) -- (-0.1, 0.6);
    \draw [->] (0.1, 3.4) -- (0.1, 0.6);
    \draw [->] (0.3, 3.5) -- (0.3, 0.5);

    \draw [->] (0.5, 0.3) -- (5.5, 0.3);
    \draw [->] (0.5, -0.3) -- (5.5, -0.3);
\end{tikzpicture}
